Nylon and nylon blend nanotubes and nanorods

Nylon nanorods and nanotubes (200 nm diameter) were fabricated by the membrane wetting technique (solvent and melt wetting) from a range of nylons (6; 6,6; 6,9; 6,10; 6,12; 11; 12, 6(3)T) and nylon blended with different dyes (Nylon Cast Blue, Nylon 6/6 Black) or with molybdenum disulfide (Nylon cast MDS). The 65-μm long nylon nanotubes and nanorods were characterized by scanning electron microscopy. The nanoscale nylon 6,6 served as an effective high surface area alternative to a nylon membrane as a solid support in a chemiluminescent assay for nylon-bound biotinylated nucleic acids based on streptavidin- alkaline phosphatase and chemiluminescent detection of the bound alkaline phosphatase label with the dioxetane substrate, CDP-Star. Layer-by-layer deposition of the cationic polymer (Sapphire-II™; Tropix) onto the nylon 6,6 nanostructures prior to UV-cross-linking with biotinylated DNA resulted in further enhancement of binding and detection of biotinylated DNA.     

尼龙6在高压退火中的晶体生长

 利用六面顶压机制备了高压退火的尼龙6样品,通过宽角X射线衍射（WAXD）、差示扫描量热（DSC）和红外光谱等手段,探索了高压退火对尼龙6结晶度以及晶体结构的变化。研究发现,在高压退火过程中尼龙6分子链段运动受到压力的限制,材料中晶体的形成主要依靠转氨基反应实现。     

Ultrasonic-assisted dyeing of Nylon-6 nanofibers

We first time report ultrasonic dyeing of the Nylon 6 nanofibers with two disperse dyes CI Disperse blue 56 and CI Disperse Red 167:1 by utilising ultrasonic energy during dyeing process. The Nylon 6 nanofibers were fabricated via electrospinning and dyed via batchwise method with and without sonication. Results revealed that ultrasonic dyeing produce higher color yield (K/S values) and substantially reduces dyeing time from 60 min for conventional dyeing to 30 min can be attributed to breakage of dye aggregate, transient cavitation near nanofiber surface and mass transfer within/between nanofibers. Color fastness results exhibited good to very good dye fixation. SEM images exhibit insignificant effect of sonication on morphology of the nanofibers. Our research results demonstrate ultrasonic dyeing as a better dyeing technique for Nylon 6 nanofibers with higher color yield and substantially reduced dyeing time.     

Development of high efficiency nanofilters made of nanofibers

Electrospinning is a fabrication process that uses an electric field to control the deposition of polymer fibers onto a target substrate. This electrostatic processing strategy can be used to fabricate fibrous polymer mats composed of fiber diameters ranging from several microns down to 100 nm or less. In this study, optimized conditions to produce nanofibers using Nylon 6 are investigated and the Nylon 6 nanofilters using nanofibers of 80–200 nm in diameter are designed and evaluated the filtration efficiency and pressure drop across the filter. When the Nylon 6 concentration is 15 wt.%, electrospun fibers have an average diameter of 80 nm, but there are many beads, and the concentration increases to 24 wt.%, the fiber diameter gradually thickens to 200 nm, but there are not any beads. When the spinning distance is small, the thinner nanofibers are produced and the more fibers are collected on the grounded electrode. The filtration efficiency of Nylon 6 nanofilters is 99.993% superior to the commercialized HEPA filter at the face velocity of 5 cm/s using 0.3 μm test particles. Even though the high pressure drops across the nanofilter, they show the potential to have the application of HEPA and ULPA grade high efficiency filter.     

Application of an ultramicrotome in SEM and TEM studies of polymeric systems with metal-containing clusters

Design features of UMTP-6 and UMTP-7 ultramicrotomes are described. The instruments were tested on the following systems: (1) polyethylene and Nylon 6 fibers treated with AgNO₃ and (2) different photographic films based on cellulose triacetate and containing silver halides.     

Effects of electrospinning process parameters on nanofibers obtained from Nylon 6 and poly (ethylene-n-butyl acrylate-maleic anhydride) elastomer blends using Johnson SB statistical distribution function

The impact strength of Nylon 6 can be further improved by blending it with ethylene-butyl acrylate-maleic anhydride elastomer. The blending is achieved in solution phase. Due to incompatibility of Nylon 6 and the elastomer, a special mixture of solvents is used to dissolve both components. The solution is electrospun, and the effects of the process parameters on the expected radii of nanofibers are investigated. The effects of process parameters such as polymer concentration in solution, electrical field, diameter of the syringe needle, feed rate, and collector geometry on nanofibers were investigated. Statistical analysis is carried out using the Johnson S_B distribution. A relation is proposed to relate the effect of the process parameters feed rate, electrical voltage, and tip to collector distance on the expected diameter of fibers. It is found that concentration and electrical field have a profound effect on the diameter of fibers compared to those of the syringe diameter and feed rate.     

PVP对Nylon 6形貌及结晶行为影响的研究

采用变温红外光谱、示差扫描量热（DSC）和偏光显微镜（POM）等方法研究了聚乙烯吡咯烷酮（PVP）与尼龙6（nylon 6）分子间的相互作用及其对nylon 6热行为及结晶形貌的影响。DSC结果表明PVP的加入明显影响了nylon 6的熔融和结晶行为：随着PVP含量增加,PVP/nylon 6共混物的结晶温度、熔融温度及结晶度均逐渐降低;POM观察显示：随着PVP含量增多,nylon 6的球晶尺寸变小、球晶逐渐变得不完善。变温红外光谱结果表明,无定形PVP分子的羰基能够与nylon 6分子的N—H基团形成新的氢键,部分破坏了nylon 6分子之间的氢键结构,从而阻碍了nylon 6分子的规整排列,使其结晶度降低并导致nylon 6结晶形貌的变化。     

金纳米-Nylon柔性膜基底的制备及其SERS性能研究

表面增强拉曼光谱（SERS）是目前最灵敏的分析技术之一,广泛应用于生命科学、材料科学、环境科学及分析化学等领域。SERS基底的特性决定了该技术的实际应用范围,是推动该技术发展的关键,高活性SERS基底的制备已经逐渐成为SERS研究领域的热点。为了获得最佳的拉曼信号,对具有特殊特性的SERS活性基底的需求一直很大。柔性SERS基底因具有良好的柔韧性,3D支架结构和表面可控的孔径大小等独特优势,在检测化合物和细菌等方面有很好的应用价值。Nylon(尼龙)柔性膜表面具有分级及多孔交错排列3D结构的特点,将固相萃取装置与特殊材料Nylon柔性膜相结合,通过改变金纳米颗粒的附着量以及金纳米颗粒与膜结合次数,制备了高SERS活性的金纳米-Nylon（Au-Nylon）柔性膜基底。研究表明,金纳米颗粒能很好地附着在Nylon纤维上,纳米颗粒与Nylon柔性膜表面等离子共振耦合作用,形成金纳米颗粒与Nylon纤维的复合体,Au-Nylon柔性膜基底的等离子共振吸收峰发生蓝移。首次处理后的Nylon纤维与其所附着的金纳米颗粒形成新的活性截留层,有助于使再次处理时金颗粒更好地附着在柔性膜表面,产生SERS“热点”效应,提高其SERS性能。利用结晶紫（CV）作为SERS探针分子,对Au-Nylon柔性膜基底SERS性能进行分析,发现CV探针分子在Au-Nylon柔性膜基底上的SERS强度随金纳米颗粒的附着量以及金纳米颗粒与膜结合次数而变化。对于面积为1 cm2的Au-Nylon柔性膜基底,当单次过滤金溶胶1 mL,与膜结合2次,总结合量2 mL时,CV探针分子的SERS信号最强,SERS活性最强。采用Au-Nylon柔性膜基底对浓度为2.5×10-5,1×10-5,1×10-6,5×10-7及1×10-7 mol·L-1的CV溶液进行的SERS检测,发现Au-Nylon柔性膜基底对CV探针分子检测极限达1×10-6 mol·L-1,增强因子达到1.0×104。此外,Au-Nylon柔性膜基底均匀性较好,相对平均偏差为11.8%。Au-Nylon柔性膜基底在微生物检测中,仍具有良好SERS活性,对金黄色葡萄球菌的SERS增强效果优于金溶胶。由此可见,研究中制备的Au-Nylon柔性具有良好的均一性,并具有较好的SERS活性,该方法简单且易批量制备,无论在化合物检测还是微生物检测中都具有良好的实际应用价值。     

MECHANISMS OF TOUGHNESS IMPROVEMENT OF SEMI-CRYSTALLINE POLYMERS

Many normally ductile semi-crystalline polymers, such as polyamide-6 (or 6,6) (Nylon), high density polyethylene (HDPE), and isotactic polypropylene (iPP) are known to be brittle under impact loading.

Some general principles for improvement of toughness of semi-crystalline polymers that rely on the reduction of plastic resistance of the cavitated matrix are presented. As typical cases, the mechanisms of the dramatic toughness jumps achievable in both Nylon and HDPE through the incorporation of either flexible rubbery particles or rigid CaCO₃ particles are discussed. In both cases these result in the establishment of a material component of reduced plastic resistance in the form of a layer of oriented crystallization of well-defined thickness around the particles. The toughness jumps occur when the average interparticle ligament thickness is reduced below a critical value, specific to the particular polymer, and the component of reduced plastic resistance percolates through the structure.     

Material Studies in a High Energy Spark Gap

The chemical interactions and physical processes occurring in a high energy spark gap with different combinations of gases, electrodes, and insulators were studied. The electrodes studied were graphite and a tungsten-copper composite; the insulators were Lexan and Blue Nylon; and the gases were N2 and SF6. The gas composition was monitored with a mass spectrometer. Spectroscopic techniques were used to observe the arc channel. The electrode surfaces were studied with several surface analysis techniques, including scanning electron microscopy, electron spectroscopy for chemical analysis, Auger electron spectroscopy, and X-ray fluorescence. The breakdown voltage distribution was examined for different material combinations. The plasma chemistry processes involving the gas, electrode, and insulator materials were found to affect the voltage self-breakdown distribution. The detailed surface analysis gave information about the nature of the chemical processes. The presence of Blue Nylon seemed to have a more adverse effect than Lexan and graphite seemed to have a narrower voltage distribution than the tungsten-copper composite.     

Tuning of electrical and structural properties of metal-polymer nanocomposite films prepared by co-evaporation technique

Nanocomposites consisting of Au and Ag nanoparticles embedded in Teflon AF 1600 (Teflon) and Nylon 6 (Nylon) matrices were prepared by a simultaneous vapor phase deposition of both the polymer and the metal. The composite films were deposited between two Au-Pd alloy electrodes prepared by sputtering onto kapton foil substrates enabling further electrical measurements. The electrical properties of the composites are strongly influenced by the metal filling factor and changes in the microstructure. At first, the dependence of the resistivity of the composites consisting of various Ag and Au nanoparticle concentrations was investigated. The resistivity is characterized by a threshold region with a critical metal filling factor. Changes in the microstructure, in particular, can occur as a result of an induced electric field in between the metal nanoparticles and a heat treatment. The I–V characteristics of Teflon AF composites for different Au concentrations were studied thoroughly. An increase in the slope of the I–V curve up to a certain voltage (breakdown voltage) was observed. This phenomenon is accompanied by the field induced tunneling of the charge carriers which enhances the conductivity. The change in conductivity was also analyzed for Nylon nanocomposites with various Au concentrations in the temperature range 20–180 °C. The observed temperature dependence is explained by activated electron tunneling between metal nanoparticles and by rearrangements in the microstructure (e.g. coalescence of metal nanoparticles). PACS  78.67.-n; 78.67.Bf     

Diffusion of 1,2,3-Benzotriazole as a Volatile Corrosion Inhibitor through Common Polymer Films Using the Molecular Dynamics Simulation Method

Diffusion of 1,2,3-benzotriazole (BT), as one of the volatile corrosion inhibitors (VCI) for copper and steel, through several polymers was investigated using molecular dynamics simulation (MD). MD were performed by employing the COMPASS force field to estimate the diffusivity of BT through polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), and Nylon 6 as potential hosts for anticorrosion film packaging purposes. The diffusion coefficients (D) of BT in these polymers were calculated by constructing an amorphous cell, each containing BT and one of these polymers. After constructing the cell, a molecular dynamics simulation was performed to calculate the mean square displacement of the BT molecule. Simulation results showed that BT can diffuse through PVC easier than the other polymers. Among these hosts the Nylon 6 had the lowest D value, implying that this polymer can maintain BT for a long time. The temperature dependence of diffusion through PE, as the most common VCI film, was studied and the activation energy (Q_d) and pre-exponential diffusion coefficient (D₀) in Arrhenius equation were calculated.     

Properties of Compatibilized Nylon 6/ABS Polymer Blends

Nylon 6/poly(acrylonitrile‐butadiene‐styrene)(ABS) blends were prepared in the molten state by a twin‐screw extruder. Maleic anhydride‐grafted polypropylene (MAP) and solid epoxy resin (bisphenol type‐A) were used as compatibilizers for these blends. The effects of compatibilizer addition to the blends were studied via tensile, torque, impact properties and morphology tests. The results showed that the additions of epoxy and MA copolymer to nylon 6/ABS blends enhanced the compatibility between nylon 6 and ABS, and this lead to improvement of mechanical properties of their blends and in a size decrease of the ABS domains.     

Contact charging between surfaces of identical insulating materials in asymmetric geometries

The charging that occurs when a pair of insulating surfaces of identical chemical composition are rubbed (i.e. triboelectric charging) remains poorly understood. It is believed that asymmetry in contact plays an important role in this charging. To study this phenomenon, we have developed an experimental methodology that asymmetrically rubs two surfaces by contacting a rotating cylinder with a stationary cylinder – the rubbing is asymmetric in that the contacting area is much greater on the rotating cylinder than on the stationary cylinder. We find that the charge transfer occurs with a spatial distribution of charge, in terms of magnitude and polarity, on the contacted area. The direction of the average charge transfer is material dependent: for Teflon–Teflon contact, the surface with the larger contacting area charges positively, but for Nylon–Nylon contact the surface with the larger contacting area charges negatively. This difference is interpreted as being due to a negatively-charged species transferred in the case of Teflon (electrons or negative ions), but a positively-charged species transferred in the case of Nylon (positive ions).     

Determination of the optical and geometrical properties of fibres having skin–core structure

A method is suggested to determine both the refractive index and the transverse sectional shape and area of fibres, having skin–core structure, at the same time for the same region of the fibre. The method depends on using a fibre rotator device attached with Pluta polarizing interference microscope, to record the variation of the fibre thickness at each angle of rotation. Nylon 6 fibres having skin–core structure were used in this study. Beck-line method was used to determine the refractive index of the skin for light vibrating parallel and perpendicular to the fibre axis. To confirm the results of the suggested method, the optical microscope was used to determine the transverse sectional shapes of bundles of nylon 6 fibres. The mean refractive indices of the skin and core of nylon 6 fibres were determined. Microinterferograms are given for illustration.     

Phase Morphology and Dynamic Mechanical Properties of Nylon 6 Based Blends Prepared via Successive In Situ Ring Opening Polymerization

Acrylonitrile butadiene styrene (ABS)/nylon 6 blends were prepared via in-situ polymerization and a compatibilization method with various blend compositions. The monomer of nylon 6 (?-caprolactam) was polymerized using activated anionic ring opening polymerization in the presence of ABS. Hexamethylene diisocyanate (HDI) and styrene maleic anhydride (SMA) were used as microactivator and macroactivator at different concentrations. Phase morphology and dynamic mechanical properties were evaluated; and the blending method was compared with ordinary reactive extruding (melt blending). In samples with dispersed structure, the dispersed particle size decreased with increasing SMA. Also, the effects of SMA at lower levels of HDI were more significant, probably due to competition between the activators in the reaction. In some of the in-situ prepared blends, even in the co-continuous structure, particles with sizes under 500 nm were observed. A noteworthy observation in micrographs was that the sizes of the dispersed particle prepared by the in situ method were less than those prepared by the compounding method. Even the uncompatibilized in situ samples had a finer particle size in comparison with the ordinary compatibilized samples. The phase inversion point was also investigated; it was affected by both micro and macro activator concentrations. At higher HDI or SMA content, a lower phase inversion concentration (φ_Nylon6) was observed. In samples with an ABS dispersed phase, after in situ compatibilization using SMA, extraction of the ABS phase did not happen easily in the given time because of the surrounding copolymer at the particles surfaces. These blends had ultra-small particles (under 200 nm). Comparison of changes in the Tg_ABS and Tg_Nylon6 showed another interesting result. While the Tgs of samples prepared by the compounding method shifted about 3°C, the Tgs of samples prepared by the in situ method shifted more obviously (around 4–30°C). This indicated the powerful compatibilization caused by the in situ polymerization and compatibilization method. All results confirmed that the in situ polymerization and compatibilization method should be considered to be useful for production of ABS/nylon 6 blends.     

Rheology,Crystallization, Mechanical and Barrier Properties of Polyamide 6/66 Nanocomposites with Exfoliated Organoclays

Nylon copolymer/clay (NC) nanocomposites were prepared using PA6/66 as a matrix and organoclay as a nanofiller through a two-step melt-compounding method. It was shown that the organoclay flakes were well exfoliated and dispersed in the PA6/66 matrix. With increasing content of organoclay, the apparent shear viscosity and the entrance pressure drop of the NC nanocomposites decreased whereas the corresponding shear activation energy increased, suggesting that the NC nanocomposites were suitable to be used in shear-flow rather than extension-flow related processes. Investigations of the crystallization behaviors of the NC nanocomposites indicated that the organoclay addition was capable of facilitating the γ-form crystal formation, which is suggested to be due to the restriction effect of the organoclay on the PA6/66 chain motion during the crystallization. Compared to the neat PA6/66, the tensile strength and elongation at break of the NC nanocomposites were both enhanced at an appropriate content of the organoclay. In addition, the NC nanocomposites exhibited enhanced barrier properties due to the high specific surface area and the homogeneous dispersion of the organoclay.     

The effect of polymer type on electric breakdown strength on a nanosecond time scale

Based on the concepts of fast polarization,effective electric field and electron impact ionization criterion,the effect of polymer type on electric breakdown strength(E BD) on a nanosecond time scale is investigated,and a formula that qualitatively characterizes the relation between the electric breakdown strength and the polymer type is derived.According to this formula,it is found that the electric breakdown strength decreases with an increase in the effective relative dielectric constants of the polymers.By calculating the effective relative dielectric constants for different types of polymers,the theoretical relation for the electric breakdown strengths of common polymers is predicted.To verify the prediction,the polymers of PE(polyethylene),PTFE(polytetrafluoroethelene),PMMA(organic glass) and Nylon are tested with a nanosecond-pulse generator.The experimental result shows E BD(PTFE) > E BD(PMMA) > E BD(Nylon) > E BD(PE).This result is consistent with the theoretical prediction.     

Performance of A 40 KJ, 60 cm long square-bore railgun

Abstract

A 60 cm long, 6 mm square bore railgun has recently been developed in pursuance of the impact fusion and related studies. Nylon projectiles (with 0.1–0.3 g mass), successfully accelerated using ～ 1 mm thick aluminum/copper metallic armatures, are recovered with front surface quite intact but slightly damaged on the back side. In the initial experiments so far, the final velocity of projectiles has been determined simply from their impact onto solid blocks and measuring the consequent displacement. The velocities of 0.2–0.5km/s so estimated, are generally in agreementwith the results expected on the basis of a simple zero-dimensional numerical simulation of the capacitor-bank driven railguns. Techniques to accurately monitor the in-bore and final projectile velocities are being tested and implemented. A maximum velocity of ～ 2 km/s for 0.5 g mass projectiles is expected after certain improvements in the system parameters.     

The effect of polymer type on electric breakdown strength on a nanosecond time scale

Based on the concepts of fast polarization, effective electric field and electron impact ionization criterion, the effect of polymer type on electric breakdown strength (E_BD) on a nanosecond time scale is investigated, and a formula that qualitatively characterizes the relation between the electric breakdown strength and the polymer type is derived. According to this formula, it is found that the electric breakdown strength decreases with an increase in the effective relative dielectric constants of the polymers. By calculating the effective relative dielectric constants for different types of polymers, the theoretical relation for the electric breakdown strengths of common polymers is predicted. To verify the prediction, the polymers of PE (polyethylene), PTFE (polytetrafluoroethelene), PMMA (organic glass) and Nylon are tested with a nanosecond-pulse generator. The experimental result shows E_BD (PTFE) > E_BD (PMMA) > E_BD (Nylon) > E_BD (PE). This result is consistent with the theoretical prediction.